A few nifty commandments

To check version on farm, when fighting schema-issues while migrating

/>get-spfarm |select name,buildversion

To check correlation id when an unexpected error has occurred

/> get-splogevent | ?{$_.Correlation -eq "CORRELATION ID"} | select Area, Category, Level, EventID, Message |Format-List

To convert users from windows-based to claims-based on a migrated webapplication.

/>convert-SPWebApplication -Identity "https://portal:80 -To Claims –RetainPermissions

References:

http://ittechnotebook.blogspot.se/2013/07/how-to-find-real-error-in-sharepoint.html

http://www.wictorwilen.se/sharepoint-2013-claims-is-the-new-black

http://www.wictorwilen.se/Post/How-Claims-encoding-works-in-SharePoint-2010.aspx

http://www.windowsecurity.com/articles-tutorials/authentication_and_encryption/Claims-Based-Identity-What-does-Mean-You-Part1.html